1. Field of the Invention
The present invention relates to a zeolite of type A and to the use thereof as a detergent builder in detergent compositions for washing various materials, fabric or otherwise. More particularly, the present invention relates to a method of determining the different mineral incrustation properties between zeolites heretofore believed to be identical, i.e., with equal particle sizes, areas, exchange capacities after fifteen minutes, and equal times to carry out one-quarter of the exchange. This is achieved by calculating a parameter k.sub.s for a given type of zeolite A and by incorporating into detergent compositions only those zeolites having a k.sub.s value above a defined minimum. The present invention further relates to detergent compositions incorporating the zeolites obtained by the above method.
2. Description of the Prior Art
In this art, sodium tripolyphosphate (STPP) has long been considered to be the best detergent builder, particularly by reason of its dispersing capability, its capability to sequester alkaline earth metal ions and its solubility, which enables same to be discarded after use without leaving any traces.
Unfortunately, its eutrophization "properties" are suspect and the compound is considered an ecological/environmental risk.
Thus, this art is replete with many and varied efforts to develop a substitute for STPP which would have the same advantages but not suffer from the defects thereof.
The natural response, therefore, was to turn to inorganic materials which were easily obtained and inexpensive, and particularly to silicoaluminates, which were well known for their cation exchanging capacity and had already been used in detergents in the past.
Synthetic zeolites, particularly of type A, too had appeared in the art and were well suited to fulfill this function, essentially because of their higher cation exchange capacity and greater purity. Moreover, based upon the knowledge that dispersion of bentonites, for example, was aided by the small size of the particles thereof, the natural reaction was to look to small particle sizes, on the order of from 0.1 to 10.mu..
Despite all of the immediately aforesaid, however, it was found that the zeolites were not suitable to replace sodium tripolyphosphate completely.
Indeed, published French Application No. 2,283,220 features the desideratum of even smaller particle sizes, despite the disadvantages which result therefrom, particularly in respect of ease of handling.
Also compare U.S. Pat. No. 4,210,416; published French Application Nos. 2,237,839, 2,291,268 and 2,396,086; published European Application Nos. 0,000,215 and 0,038,591.